Test/Investigation
Acetylcholine Receptor Ab (ACRA)
Site(s) or Laboratory offering Test/Investigation
Referral laboratory
Units
nmol/L
Also Known as/Frequency of Test
ACR; ACHR; Myasthenia antibody; Motor end plate antibody; MG antibody, ACRA
Indications
Acetylcholine receptor antibodies are a highly sensitive and specific marker for generalised myasthenia gravis (80-90% sensitivity); up to 90% of generalised MG cases are ACHR positive for ACHR antibodies whilst in pure ocular MG up to 50% of patients are positive Level of antibodies do not correlate with disease activity, so repeated testing is not indicated. In patients with suspected MG who are negative for ACRA, anti-MuSK (muscle-specific receptor tyrosine kinase) antibodies may be indicated.
Comments/Precautions
Plasma NOT acceptable. Referred outside of EPA
Sample type
Serum
Turnaround times (TAT) Urgent/Routine/GP or OPD
2 weeks
Reference intervals (adult unless stated)
<0.2nmol/L Negative
0.2 – 0.4 nmol/L Doubtful
>0.4nmol/L Positive